Code refactoring: Empty border styles

Excel prefer <border><left/><right/><top/><bottom/><diagonal/></border> to
<border/>

src/xlsx/xlsxformat.cpp

@@ -1233,7 +1233,7 @@ int Format::theme() const
  */
 QVariant Format::property(int propertyId, const QVariant &defaultValue) const
 {
-    if (d->property.contains(propertyId))
+    if (d && d->property.contains(propertyId))
         return d->property[propertyId];
     return defaultValue;
 }

src/xlsx/xlsxstyles.cpp

@@ -505,17 +505,14 @@ void Styles::writeBorder(QXmlStreamWriter &writer, const Format &border, bool is
             writer.writeAttribute(QStringLiteral("diagonalDown"), QStringLiteral("1"));
         }
     }
-    if (border.hasProperty(FormatPrivate::P_Border_LeftStyle))
+
-        writeSubBorder(writer, QStringLiteral("left"), border.leftBorderStyle(), border.property(FormatPrivate::P_Border_LeftColor).value<XlsxColor>());
+    writeSubBorder(writer, QStringLiteral("left"), border.leftBorderStyle(), border.property(FormatPrivate::P_Border_LeftColor).value<XlsxColor>());
-    if (border.hasProperty(FormatPrivate::P_Border_RightStyle))
+    writeSubBorder(writer, QStringLiteral("right"), border.rightBorderStyle(), border.property(FormatPrivate::P_Border_RightColor).value<XlsxColor>());
-        writeSubBorder(writer, QStringLiteral("right"), border.rightBorderStyle(), border.property(FormatPrivate::P_Border_RightColor).value<XlsxColor>());
+    writeSubBorder(writer, QStringLiteral("top"), border.topBorderStyle(), border.property(FormatPrivate::P_Border_TopColor).value<XlsxColor>());
-    if (border.hasProperty(FormatPrivate::P_Border_TopStyle))
+    writeSubBorder(writer, QStringLiteral("bottom"), border.bottomBorderStyle(), border.property(FormatPrivate::P_Border_BottomColor).value<XlsxColor>());
-        writeSubBorder(writer, QStringLiteral("top"), border.topBorderStyle(), border.property(FormatPrivate::P_Border_TopColor).value<XlsxColor>());
-    if (border.hasProperty(FormatPrivate::P_Border_BottomStyle))
-        writeSubBorder(writer, QStringLiteral("bottom"), border.bottomBorderStyle(), border.property(FormatPrivate::P_Border_BottomColor).value<XlsxColor>());
 
     //Condition DXF formats don't allow diagonal style
-    if (!isDxf && border.hasProperty(FormatPrivate::P_Border_DiagonalStyle))
+    if (!isDxf)
         writeSubBorder(writer, QStringLiteral("diagonal"), border.diagonalBorderStyle(), border.property(FormatPrivate::P_Border_DiagonalColor).value<XlsxColor>());
 
     if (isDxf) {

tests/auto/styles/tst_stylestest.cpp

@@ -37,6 +37,7 @@ void StylesTest::testEmptyStyle()
 
 //    QVERIFY2(xmlData.contains("<cellXfs count=\"1\"><xf numFmtId=\"0\" fontId=\"0\" fillId=\"0\" borderId=\"0\" xfId=\"0\"/></cellXfs>"), "Must have one cell style");
     QVERIFY2(xmlData.contains("<cellXfs count=\"1\"><xf xfId=\"0\"/></cellXfs>"), "Must have one cell style");
+    QVERIFY2(xmlData.contains("<border><left/><right/><top/><bottom/><diagonal/></border>"), "Excel don't simply generate <border/>, through it works");
 }
 
 void StylesTest::testAddXfFormat()
@@ -92,7 +93,7 @@ void StylesTest::testWriteBorders()
 
     QByteArray xmlData = styles.saveToXmlData();
 
-    QVERIFY(xmlData.contains("<border><right style=\"thin\">"));
+    QVERIFY(xmlData.contains("<border><left/><right style=\"thin\">"));
 }
 
 void StylesTest::testReadFonts()